Plant growth regulation

ABSTRACT

The present invention relates to a method for improving the plant growth regulation of and/or enhancing dicotyledonous crop plants, by applying to the plants trinexapac-ethyl and prohexadione-calcium, and to use of a composition comprising the same.

This application is a 371 of International Application No. PCT/EP2010/007130 filed Nov. 24, 2010, which claims priority to GB 0920894.3 filed Nov. 27, 2009, and GB 1004176.2 filed Mar. 12, 2010, the contents of which are incorporated herein by reference.

The present invention relates to a method for improving the plant growth regulation of crop plants, by applying to the crop plants a mixture of a trinexapac-ethyl and prohexadione-calcium, and to a composition comprising the same.

Plant growth regulators are often used to regulate the growth and development of crop plants. For example, plant growth regulators are used to slow the development of a crop (such as oil seed rape) so that it flowers at a desired time, reduce the height of a crop (such as in cereals) so that it is less susceptible to lodging, increase nitrogen efficiency, regulate flowering and fruit set of a crop (such as fruit trees), and slow turfgrass growth rate to reduce mowing frequency.

There are several different classes of plant growth regulator. Known classes include azoles (such as uniconazole, and paclobutrazol), cyclohexane carboxylates (such as trinexapac-ethyl, and prohexadione-calcium), pyrimidinyl carbinols (such as flurprimidol, and ancymidol), quarternary ammoniums (such as chlormequat-chloride, and mepiquat-chloride), and sulphonyl-amino phenyl-acetamides (such as mefluidide).

Plant growth regulators operate by various modes of action. For example, onium-type plant growth retardants such as chlormequat-chloride and mepiquat-chloride, that possess a positively charged ammonium, phosphonium or sulphonium group, function by blocking the synthesis of gibberellin early in the biosynthetic pathway. Growth retardants comprising a nitrogen-containing heterocycle, such as flurprimidol, paclobutrazol and uniconazole-P, act as inhibitors of monooxygenases that catalyse oxidative steps in gibberellin biosynthesis. Structural mimics of 2-oxoglutaric acid, such as the acylcyclohexanediones trinexapac-ethyl and prohexadione-calcium, interfere with the late steps of gibberellin biosynthesis. Other plant growth regulators, such as mefluidide, inhibit cell division and differentiation.

Plant growth regulators such as trinexapac-ethyl are commonly used on crops to reduce the risk of lodging through stem thickening and shortening, and improved rooting.

In some cases, active ingredients have been shown to be more effective when mixed with other active ingredients compared to when applied individually, and this is referred to as “synergism”, since the combination demonstrates a potency or activity level exceeding that which it would be expected to have based on knowledge of the individual potencies of the components. It has been found that combinations of trinexapac-ethyl and prohexadione-calcium provide a synergistic growth regulation effect. Such combinations are also useful in providing an improved plant growth regulation effect in crop plants because of the strong plant growth regulation effect of trinexapac-ethyl combined with the fast acting plant growth regulation effect of prohexadione-calcium. Additionally, co-application of two plant growth regulating compounds results in a growth regulation effect that is the same or better than that of either compound applied alone, using a lower concentration of each plant growth regulator. This enables the composition to be applied at an earlier growth stage of the crop without causing phytotoxicity.

According to the present invention, there is provided a method for regulating the growth of crop plants, comprising applying to the plants, plant parts, plant propagation material, or a plant growing locus, trinexapac-ethyl and prohexadione-calcium in a synergistically effective amount.

The term ‘regulating the growth’ includes restricting shoot growth, promoting root growth, stunting, and the like.

The term ‘plants’ refers to all physical parts of a plant, including seeds, seedlings, saplings, roots, tubers, stems, stalks, foliage and fruits.

The term ‘plant propagation material’ denotes generative parts of the plant, such as seeds, which can be used for the multiplication of the latter, and vegetative material, such as cuttings or tubers, for example potatoes. In particular, it includes seeds (in the strict sense), roots, fruits, tubers, bulbs, rhizomes and parts of plants. Germinated plants and young plants which are to be transplanted after germination or after emergence from the soil, may also be mentioned—these young plants may be protected before transplantation by a total or partial treatment by immersion. Suitably “plant propagation material” is understood to denote seeds.

The term ‘plant growing locus’ is intended to embrace the place on which the plants are growing, where the plant propagation materials of the plants are sown or where the plant propagation materials of the useful plants will be placed into the soil. An example for such a locus is a field, on which crop plants are growing.

The present invention also provides a method for enhancing crop plants, comprising applying to the plants, plant parts, plant propagation material, or a plant growing locus, trinexapac-ethyl and prohexadione-calcium in a synergistically effective amount.

According to the present invention, ‘enhancing crop plants’ means improving plant quality and/or plant vigour and/or tolerance to stress factors, any of which may lead to increased yield. In one embodiment, the present invention relates to a method for improving plant yield, comprising applying to the plant, plant part, plant propagation material, or a plant growing locus, trinexapac-ethyl and prohexadione-calcium. Such improved yield may be as a result of improved root growth. In a further embodiment, the present invention relates to a method for improving plant vigour and/or plant quality, and/or plant tolerance to stress factors, comprising applying to the plant, plant part, plant propagation material, or a plant growing locus, trinexapac-ethyl and prohexadione calcium.

According to the present invention, an improvement in plant vigour means that certain traits are improved qualitatively or quantitatively when compared with the same trait in a control plant which has been grown under the same conditions in the absence of the method of the invention. Such traits include, but are not limited to, early and/or improved germination, improved emergence, the ability to use less seeds, increased root growth, a more developed root system, increased shoot growth, increased tillering, stronger tillers, more productive tillers, increased or improved plant stand, less plant verse (lodging), an increase and/or improvement in plant height, an increase in plant weight (fresh or dry), bigger leaf blades, greener leaf colour, increased pigment content, increased photosynthetic activity, earlier flowering, homogenous flowering, longer panicles, early grain maturity, increased seed, fruit or pod size, increased pod or ear number, increased seed number per pod or ear, increased seed mass, enhanced seed filling, less dead basal leaves, delay of senescence, improved vitality of the plant and/or less inputs needed (e.g. less fertiliser, water and/or labour needed). A plant with improved vigour may have an increase in any of the aforementioned traits or any combination or two or more of the aforementioned traits. Suitably, the method of the present invention increases plant height, plant weight and/or provides enhanced germination.

According to the present invention, an improvement in plant quality means also that certain traits are improved qualitatively or quantitatively when compared with the same trait in a control plant which has been grown under the same conditions in the absence of the method of the invention. Such traits include, but are not limited to, improved visual appearance of the plant (e.g. improved colour, density, uniformity, compactness), reduced ethylene (reduced production and/or inhibition of reception), improved quality of harvested material, e.g. seeds, fruits, leaves, vegetables (such improved quality may manifest as improved visual appearance of the harvested material, improved carbohydrate content (e.g. increased quantities of sugar and/or starch, improved sugar acid ratio, reduction of reducing sugars, increased rate of development of sugar), improved protein content, improved oil content and composition, improved nutritional value, reduction in anti-nutritional compounds, improved organoleptic properties (e.g. improved taste) and/or improved consumer health benefits (e.g. increased levels of vitamins and anti-oxidants)), improved post-harvest characteristics (e.g. enhanced shelf-life and/or storage stability, easier processability, easier extraction of compounds) and/or improved seed quality (e.g. for use in following seasons). A plant with improved quality may have an increase in any of the aforementioned traits or any combination or two or more of the aforementioned traits.

According to the present invention, an improved tolerance to stress factors means that certain traits are improved qualitatively or quantitatively when compared with the same trait in a control plant which has been grown under the same conditions in the absence of the method of the invention. Such traits include, but are not limited to, an increased tolerance and/or resistance to abiotic stress factors which cause sub-optimal growing conditions such as drought (e.g. any stress which leads to a lack of water content in plants, a lack of water uptake potential or a reduction in the water supply to plants), cold exposure, heat exposure, osmotic stress, UV stress, flooding, increased salinity (e.g. in the soil), increased mineral exposure, ozone exposure, high light exposure and/or limited availability of nutrients (e.g. nitrogen and/or phosphorus nutrients). A plant with improved tolerance to stress factors may have an increase in any of the aforementioned traits or any combination or two or more of the aforementioned traits. In the case of drought and nutrient stress, such improved tolerances may be due to, for example, more efficient uptake, use or retention of water and nutrients. Suitably, the method of the present invention increases tolerance of plants to drought.

Any or all of the above crop enhancements may lead to an improved yield by improving e.g. plant physiology, plant growth and development and/or plant architecture. In the context of the present invention ‘yield’ includes, but is not limited to, (i) an increase in biomass production, grain yield (e.g. grain size, grain number, grain density), starch content, oil content and/or protein content, which may result from (a) an increase in the amount produced by the plant per se or (b) an improved ability to harvest plant matter, (ii) an improvement in the composition of the harvested material (e.g. improved sugar acid ratios, improved oil composition, increased nutritional value, reduction of anti-nutritional compounds, increased consumer health benefits) and/or (iii) an increased/facilitated ability to harvest the crop, improved processability of the crop and/or better storage stability/shelf life. Increased yield of an agricultural plant means that, where it is possible to take a quantitative measurement, the yield of a product of the respective plant is increased by a measurable amount over the yield of the same product of the plant produced under the same conditions, but without application of the present invention. According to the present invention, it is preferred that the yield be increased by at least 0.5%, more preferred at least 1%, even more preferred at least 2%, still more preferred at least 4%, preferably 5% or even more.

Any or all of the above crop enhancements may also lead to an improved utilisation of land, i.e. land which was previously unavailable or sub-optimal for cultivation may become available. For example, plants which show an increased ability to survive in drought conditions, may be able to be cultivated in areas of sub-optimal rainfall, e.g. perhaps on the fringe of a desert or even the desert itself.

The term ‘synergistically effective amount’ indicates the quantity of such compounds which is capable of modifying the effect on the growth of plants, where said effect is greater than the sum of the effects obtained by applying each of the compounds individually.

In the present invention, the mixture ratio of trinexapac-ethyl to prohexadione-calcium at which the growth regulation effect is synergistic lies within the range from about 1:1000 to about 1000:1 by weight. Suitably, the mixture ratio of trinexapac-ethyl to prohexadione-calcium is from about 1:100 to about 100:1 by weight. More suitably, the mixture ratio of trinexapac-ethyl to prohexadione-calcium is from about 10:1 to about 1:10 by weight. More suitably, the mixture ratio is from about 5:1 to 1:5; more suitably still it is from 2:1 to 1:2.

The rate of application of the compounds of the present invention may vary within wide limits and depends upon the nature of the soil, the method of application, the target insect pest to be controlled, the prevailing climatic conditions, and other factors governed by the method of application and the time of application. The compounds of the present invention are generally each applied at a rate of 0.001 to 4 kg/ha, especially from 0.005 to 1 kg/ha, in particular of 0.01 to 0.5 kg/ha. In particular, the compounds of the present invention are each applied at a rate of 0.01 to 0.2 kg/ha. Suitably, the trinexapac-ethyl is applied at a rate from about 25 to about 100 g ai/ha, and prohexadione-calcium is applied at a rate from about 25 to about 100 g ai/ha.

If desired, it is possible to use one or more additional plant growth regulators in combination with trinexapac-ethyl and prohexadione-calcium in accordance with the present invention.

The method of the present invention may be applied to any dicotyledon crops such as beet (such as sugar beet or fodder beet); fruits (such as pomes, stone fruits or soft fruits, for example apples, pears, plums, peaches, almonds, cherries, strawberries, raspberries or black-berries); leguminous plants (such as beans, lentils, peas or soybeans); oil plants (such as rape, mustard, poppy, olives, sunflowers, coconut, castor oil plants, cocoa beans or groundnuts); cucumber plants (such as marrows, cucumbers or melons); fibre plants (such as cotton, flax, hemp or jute); citrus fruit (such as oranges, lemons, grapefruit or mandarins); vegetables (such as spinach, lettuce, cabbages, carrots, tomatoes, potatoes, cucurbits or paprika); lauraceae (such as avocados, cinnamon or camphor); tobacco; nuts; coffee; tea; vines; hops; durian; bananas; natural rubber plants; and ornamentals (such as flowers, shrubs, broad-leaved trees or evergreens, for example conifers). This list does not represent any limitation.

In one embodiment, the crop plants are oil plants. In particular, the crop plants are oil seed rape plants.

Crops include those that have been rendered tolerant to herbicides like bromoxynil or classes of herbicides (such as HPPD inhibitors, ALS inhibitors (for example primisulfuron, prosulfuron and trifloxysulfuron), EPSPS (5-enol-pyrovyl-shikimate-3-phosphate-synthase) inhibitors, GS (glutamine synthetase) inhibitors or PPO (protoporphyrinogen-oxidase) inhibitors) as a result of conventional methods of breeding or genetic engineering. An example of a crop that has been rendered tolerant to imidazolinones, e.g. imazamox, by conventional methods of breeding (mutagenesis) is Clearfield® summer rape (Canola). Examples of crops that have been rendered tolerant to herbicides or classes of herbicides by genetic engineering methods include glyphosate- and glufosinate-resistant maize varieties commercially available under the trade names RoundupReady®, Herculex IÒ and LibertyLink®. Crops also includes plants that have been transformed by the use of recombinant DNA techniques so that they are capable of synthesising one or more selectively acting toxins, such as are known, for example, from toxin-producing bacteria, especially those of the genus Bacillus. Crops also includes plants which have been transformed by the use of recombinant DNA techniques so that they are capable of synthesising antipathogenic substances having a selective action, such as, for example, the so-called “pathogenesis-related proteins”. Examples of such antipathogenic substances and transgenic plants capable of synthesising such antipathogenic substances are known, for example, from EP-A-0 392 225, WO 95/33818, and EP-A-0 353 191. The methods of producing such transgenic plants are generally known to the person skilled in the art and are described, for example, in the publications mentioned above.

Examples of monocotyledon crops include cereals (wheat, millet, sorghum, rye, triticale, oats, barley, teff, spelt, buckwheat, fonio and quinoa), rice, maize (corn), turfgrass and sugar cane.

The trinexapac-ethyl and prohexadione-calcium of the present invention may be applied either simultaneously or sequentially in any order. If administered sequentially, the components may be administered in any order in a suitable timescale, for example, with no longer than 1 month, no longer than 1 week, or no longer than 24 hours between the time of administering the first component and the time of administering the last component. Suitably, the components are administered within a timescale of a few hours, such as one hour. If the trinexapac-ethyl and prohexadione-calcium are administered simultaneously, they may be administered separately or as a tank mix or as a pre-formulated mixture. In one embodiment the mixture or composition of the present invention may be applied to the crop plants as a seed treatment prior to planting.

When the method of the present invention refers to the application to crop plants of a co-formulated composition, the composition comprises both trinexapac-ethyl and prohexadione-calcium. The compounds may be homogeneously mixed together with other formulation components necessary to make the desired formulation type, as is known to those skilled in the art.

In one embodiment of the present invention, the trinexapac-ethyl and prohexadione-calcium are applied in the form of a composition comprising an agriculturally acceptable carrier.

The compounds of the present invention may be used in unmodified form, but are generally formulated into compositions using formulation adjuvants, such as carriers, solvents and surface-active substances. The formulations can be in various physical forms, for example dusting powders, gels, wettable powders, water-dispersible granules, water-dispersible tablets, effervescent compressed tablets, emulsifiable concentrates, microemulsifiable concentrates, oil-in-water emulsions, oil flowables, aqueous dispersions, oil dispersions, suspoemulsions, capsule suspensions, emulsifiable granules, soluble liquids, water-soluble concentrates (with water or a water-miscible organic solvent as carrier), or impregnated polymer films. Such formulations can either be used directly or are diluted prior to use. Diluted formulations can be prepared, for example, with water, liquid fertilizers, micro-nutrients, biological organisms, oil or solvents. These formulations may contain as little as about 0.5% to as much as about 95% or more by weight of active ingredient. The optimum amount for any given compound will depend on formulation, application equipment and nature of the plants to be controlled.

Wettable powders are in the form of finely divided particles which disperse readily in water or other liquid carriers. The particles contain the active ingredient retained in a solid matrix. Typical solid matrices include fuller's earth, kaolin clays, silicas and other readily wet organic or inorganic solids. Wettable powders normally contain about 5% to about 95% of the active ingredient plus a small amount of wetting, dispersing or emulsifying agent.

Emulsifiable concentrates are homogeneous liquid compositions dispersible in water or other liquid and may consist entirely of the active compound with a liquid or solid emulsifying agent, or may also contain a liquid carrier, such as xylene, heavy aromatic naphthas, isophorone and other non-volatile organic solvents. In use, these concentrates are dispersed in water or other liquid and normally applied as a spray to the area to be treated. The amount of active ingredient may range from about 0.5% to about 95% of the concentrate.

Granular formulations include both extrudates and relatively coarse particles and are usually applied without dilution to the area in which suppression of vegetation is desired. Typical carriers for granular formulations include fertiliser, sand, fuller's earth, attapulgite clay, bentonite clays, montmorillonite clay, vermiculite, perlite, calcium carbonate, brick, pumice, pyrophyllite, kaolin, dolomite, plaster, wood flour, ground corn cobs, ground peanut hulls, sugars, sodium chloride, sodium sulphate, sodium silicate, sodium borate, magnesia, mica, iron oxide, zinc oxide, titanium oxide, antimony oxide, cryolite, gypsum, diatomaceous earth, calcium sulphate and other organic or inorganic materials which absorb or which can be coated with the active compound. Particularly suitable is a fertiliser granule carrier. Granular formulations normally contain about 5% to about 25% active ingredients which may include surface-active agents such as heavy aromatic naphthas, kerosene and other petroleum fractions, or vegetable oils; and/or stickers such as dextrins, glue or synthetic resins. The granular substrate material can be one of the typical carriers mentioned above and/or can be a fertiliser material e.g. urea/formaldehyde fertilisers, ammonium, liquid nitrogen, urea, potassium chloride, ammonium compounds, phosphorus compounds, sulphur, similar plant nutrients and micronutrients and mixtures or combinations thereof. The trinexapac-ethyl and prohexadione-calcium may be homogeneously distributed throughout the granule or may be spray impregnated or absorbed onto the granule substrate after the granules are formed.

Encapsulated granules are generally porous granules with porous membranes sealing the granule pore openings, retaining the active species in liquid form inside the granule pores. Granules typically range from 1 millimeter to 1 centimeter, preferably 1 to 2 millimeters in diameter. Granules are formed by extrusion, agglomeration or prilling, or are naturally occurring. Examples of such materials are vermiculite, sintered clay, kaolin, attapulgite clay, sawdust and granular carbon. Shell or membrane materials include natural and synthetic rubbers, cellulosic materials, styrene-butadiene copolymers, polyacrylonitriles, polyacrylates, polyesters, polyamides, polyureas, polyurethanes and starch xanthates.

Dusts are free-flowing admixtures of the active ingredient with finely divided solids such as talc, clays, flours and other organic and inorganic solids which act as dispersants and carriers.

Microcapsules are typically droplets or granules of the active material enclosed in an inert porous shell which allows escape of the enclosed material to the surroundings at controlled rates. Encapsulated droplets are typically about 1 to 50 microns in diameter. The enclosed liquid typically constitutes about 50 to 95% of the weight of the capsule and may include solvent in addition to the active compound.

Other useful formulations for plant growth regulation applications include simple solutions of the active ingredients in a solvent in which it is completely soluble at the desired concentration, such as acetone, alkylated naphthalenes, xylene and other organic solvents. Pressurised sprayers, wherein the active ingredient is dispersed in finely-divided form as a result of vaporisation of a low boiling dispersant solvent carrier, may also be used.

Many of the formulations described above include wetting, dispersing or emulsifying agents. Examples are alkyl and alkylaryl sulphonates and sulphates and their salts, polyhydric alcohols; polyethoxylated alcohols, esters and fatty amines. These agents, when used, normally comprise from 0.1% to 15% by weight of the formulation.

Suitable agricultural adjuvants and carriers, either formulated together and/or added separately, that are useful in formulating the compositions of the invention in the formulation types described above are well known to those skilled in the art. Suitable examples of the different classes are found in the non-limiting list below.

Liquid carriers that can be employed include water, toluene, xylene, petroleum naphtha, crop oils, AMS; acetone, methyl ethyl ketone, cyclohexanone, acetic anhydride, acetonitrile, acetophenone, amyl acetate, 2-butanone, chlorobenzene, cyclohexane, cyclohexanol, alkyl acetates, diacetonalcohol, 1,2-dichloropropane, diethanolamine, p-diethylbenzene, diethylene glycol, diethylene glycol abietate, diethylene glycol butyl ether, diethylene glycol ethyl ether, diethylene glycol methyl ether, N,N-dimethyl formamide, dimethyl sulfoxide, 1,4-dioxane, dipropylene glycol, dipropylene glycol methyl ether, dipropylene glycol dibenzoate, diproxitol, alkyl pyrrolidinone, ethyl acetate, 2-ethyl hexanol, ethylene carbonate, 1,1,1-trichloroethane, 2-heptanone, alpha pinene, d-limonene, ethylene glycol, ethylene glycol butyl ether, ethylene glycol methyl ether, gamma-butyrolactone, glycerol, glycerol diacetate, glycerol monoacetate, glycerol triacetate, hexadecane, hexylene glycol, isoamyl acetate, isobornyl acetate, isooctane, isophorone, isopropyl benzene, isopropyl myristate, lactic acid, laurylamine, mesityl oxide, methoxy-propanol, methyl isoamyl ketone, methyl isobutyl ketone, methyl laurate, methyl octanoate, methyl oleate, methylene chloride, m-xylene, n-hexane, n-octylamine, octadecanoic acid, octyl amine acetate, oleic acid, oleylamine, o-xylene, phenol, polyethylene glycol (PEG400), propionic acid, propylene glycol, propylene glycol monomethyl ether, p-xylene, toluene, triethyl phosphate, triethylene glycol, xylene sulfonic acid, paraffin, mineral oil, trichloroethylene, perchloroethylene, ethyl acetate, amyl acetate, butyl acetate, methanol, ethanol, isopropanol, and higher molecular weight alcohols such as amyl alcohol, tetrahydrofurfuryl alcohol, hexanol, octanol, etc. ethylene glycol, propylene glycol, glycerine, N-methyl-2-pyrrolidinone, and the like. Water is generally the carrier of choice for the dilution of concentrates.

Suitable solid carriers include talc, titanium dioxide, pyrophyllite clay, silica, attapulgite clay, kieselguhr, chalk, diatomaxeous earth, lime, calcium carbonate, bentonite clay, fuller's earth, fertiliser, cotton seed hulls, wheat flour, soybean flour, pumice, wood flour, walnut shell flour, lignin and the like.

A broad range of surface-active agents are advantageously employed in both said liquid and solid compositions, especially those designed to be diluted with carrier before application. The surface-active agents can be anionic, cationic, non-ionic or polymeric in character and can be employed as emulsifying agents, wetting agents, suspending agents or for other purposes. Typical surface active agents include salts of alkyl sulfates, such as diethanolammonium lauryl sulphate; alkylarylsulfonate salts, such as calcium dodecylbenzenesulfonate; alkylphenol-alkylene oxide addition products, such as nonylphenol-C.sub. 18 ethoxylate; alcohol-alkylene oxide addition products, such as tridecyl alcohol-C.sub. 16 ethoxylate; soaps, such as sodium stearate; alkylnaphthalenesulfonate salts, such as sodium dibutylnaphthalenesulfonate; dialkyl esters of sulfosuccinate salts, such as sodium di(2-ethylhexyl) sulfosuccinate; sorbitol esters, such as sorbitol oleate; quaternary amines, such as lauryl trimethylammonium chloride; polyethylene glycol esters of fatty acids, such as polyethylene glycol stearate; block copolymers of ethylene oxide and propylene oxide; and salts of mono and dialkyl phosphate esters.

Other adjuvants commonly utilized in agricultural compositions include crystallisation inhibitors, viscosity modifiers, suspending agents, spray droplet modifiers, pigments, antioxidants, foaming agents, light-blocking agents, compatibilizing agents, antifoam agents, sequestering agents, neutralising agents and buffers, corrosion inhibitors, dyes, odorants, spreading agents, penetration aids, micronutrients, emollients, lubricants, sticking agents, and the like. The compositions can also be formulated with liquid fertilizers or solid, particulate fertiliser carriers such as ammonium nitrate, urea and the like.

Also, the present invention may optionally include one or more additional pesticides such as insecticides, nematicides, fungicides or herbicides or additional plant growth regulators. Co-application of pesticides with the present invention has the added benefit of minimising farmer time spent applying products to crops, since only a single application may be required to both provide growth regulation and control pests.

According to the present invention, there is provided the use of a composition comprising a synergistically effective amount of trinexapac-ethyl and prohexadione-calcium, for regulating the growth of and/or enhancing crop plants, as described above. In one embodiment, the crop plants are dicotyledonous plants.

Compositions of the present invention may contain from about 0.001% to about 99% by weight active ingredients. Suitably, the composition contains from about 0.001% to about 50% by weight active ingredients. More suitably, the composition contains from about 0.001% to about 10% by weight active ingredients. More suitably, the composition contains from about 0.001% to about 1% by weight active ingredients. If the formulation is in the form of a concentrate, requiring dilution with water before use, it will contain a higher amount of active ingredients than a composition that is ready to use without dilution.

Although the invention has been described with reference to preferred embodiments and examples thereof, the scope of the present invention is not limited only to those described embodiments. As will be apparent to persons skilled in the art, modifications and adaptations to the above-described invention can be made without departing from the spirit and scope of the invention, which is defined and circumscribed by the attached claims.

EXAMPLES Example 1 Plant Growth Regulation on Cereals

Plants were grown under greenhouse conditions and sprayed at growth stage 30-32 (start of stem elongation) of cereal plants with a boom sprayer. Trinexapac-ethyl (treatment A) was applied as Moddus® ME250 formulation, and Prohexadione-Ca (treatment B) was applied as Viviful® WG10 formulation with a standard flat fan nozzle at 200 l/ha spray volume. 13 days after application the plant growth reduction (% GR) of the shoot (leaves and stem) was evaluated visually compared to the untreated control. The expected plant growth reduction was calculated according to Colby (Colby 1967, Weeds 15, 20-22) and compared to evaluation data of sprayed plants.

Spring-barley Winter-barley Winter-wheat Spring-wheat Rate Pasadena Hasso Arina Lona Treatment (g a.i./ha) % GR Colby % GR Colby % GR Colby % GR Colby A 50 0.0 — 5.0 — 5.0 — 3.3 — A 25 0.0 — 0.0 — 0.0 — 1.7 — B 50 1.7 — 5.0 — 3.3 — 3.3 — B 25 0.0 — 0.0 — 0.0 — 0.0 — A + B 50 + 25 8.3 0.0 11.7 5.0 13.3 5.0 11.7 3.3 A + B 50 + 50 15.0 1.7 16.7 9.8 13.3 8.2 11.7 6.6 A + B 25 + 25 6.7 0.0 6.7 0.0 5.0 0.0 3.3 1.7 A + B 25 + 50 11.7 1.7 11.7 5.0 18.3 3.3 11.7 4.9

The data shows that mixtures of trinexapac-ethyl and prohexadione-calcium result in a higher plant growth reduction that one would expect based on the activity of each active ingredient alone, indicating a synergistic effect.

Example 2 Plant Growth Regulation on Corn

Corn plants of 4 different varieties were grown under greenhouse conditions and sprayed at growth stage 13 (3 leaves unfolded) with a boom sprayer. Trinexapac-ethyl was applied as Moddus® ME250 formulation, and Prohexadion-Ca was applied as Viviful® WG 10 formulation with a standard flat fan nozzle at 200 l/ha spray volume. 33 days after application the plant growth reduction (% GR) of the shoot (leaves and stem) was evaluated visually compared to the untreated control. The expected plant growth reduction was calculated according to Colby (Colby 1967, Weeds 15, 20-22) and compared to evaluation data of sprayed plants.

Corn Corn Corn Corn Rate ECO5133 LG22.65 Maeva Ronaldinio Treatment (g a.i./ha) % GR Colby % GR Colby % GR Colby % GR Colby A 100 6.7 — 11.7 — 6.7 — 3.3 — A 50 1.7 — 3.3 — 3.3 — 0.0 — A 25 1.7 — 0.0 — 1.7 — 0.0 — B 100 0.0 — 13.3 — 18.3 — 1.7 — B 50 0.0 — 1.7 — 5.0 — 0.0 — B 25 0.0 — 0.0 — 1.7 — 0.0 — A + B 100 + 50  16.7 6.7 20.0 13.1 23.3 11.3 8.3 3.3 A + B 50 + 25 3.3 1.7 8.3 3.3 15.0 4.9 0.0 0.0 A + B  50 + 100 13.3 1.7 15.0 16.2 20.0 21.1 8.3 1.7 A + B 25 + 50 1.7 1.7 6.7 1.7 13.3 6.6 3.3 0.0

The data shows that mixtures of trinexapac-ethyl and prohexadione-calcium result in a higher plant growth reduction that one would expect based on the activity of each active ingredient alone, indicating a synergistic effect. 

The invention claimed is:
 1. A method for regulating the growth of and/or enhancing dicotyledonous crop plants, comprising applying to the plants, plant parts, plant propagation material, or a plant growing locus, trinexapac-ethyl and prohexadione-calcium; wherein the trinexapac-ethyl and prohexadione-calcium are applied in a synergistically effective amount.
 2. A method according to claim 1, wherein the crop plants are oil plants.
 3. A method according to claim 2, wherein the crop plants are oil seed rape plants.
 4. A method according to claim 1, wherein the trinexapac-ethyl and prohexadione-calcium are applied to the plant in a weight ratio from about 5:1 to about 1:5.
 5. A method according to claim 1, wherein the trinexapac-ethyl is applied at a rate from about 10 to about 200 g ai/ha.
 6. A method according to claim 1, wherein the prohexadione-calcium is applied at a rate from about 10 to about 200 g ai/ha.
 7. A method according to claim 1, wherein the trinexapac-ethyl and prohexadione-calcium are applied sequentially.
 8. A method according to claim 1, wherein the trinexapac-ethyl and prohexadione-calcium are applied simultaneously.
 9. A method according to claim 1, wherein the trinexapac-ethyl and prohexadione-calcium are applied in the form of a composition comprising an agriculturally acceptable carrier.
 10. A method according to claim 1, wherein the enhancement is improved plant yield.
 11. A method according to claim 1, wherein the enhancement is improved plant vigour and/or plant quality, and/or plant tolerance to stress factors.
 12. A method according to claim 11, wherein the enhancement is improved tolerance to drought conditions.
 13. A method for regulating the growth of and/or enhancing dicotyledonous crop plants, the method comprising applying to the plants, plant parts, plant propagation material, or a plant growing locus, a composition comprising a synergistically effective amount of trinexapac-ethyl and prohexadione-calcium. 